What’s wrong with my grumichama?

[Guoyang Gao]

I bought a grumichama tree 3 years ago when it was 2 years old from a nursery in GuangZhou. It looked fine when first arriving and I planted it in a big pottery container. However, after a year or two, it hadn't grown too much. The leaves, especially the sprouts looked unhealthier day by day. Some new sprouts even withered before spreading. Just a few flower buds appeared in last March but all dropped down. (no flower bud this year). Last autumn, I transplanted it into a bigger pot and replaced the original soil with something better, finding that the roots didn't develop very well.

There is a sub-tropical mountain climate in my town which has warm but dry winter and spring.The relative air humidity often drops to 20%~30% in dry season. The annual mean temperature is about 17.2 degree centigrade. The yearly precipitation is about 1000 mm. The rainy season usually lasts from late May to early October.

It is said that grumichama tree could only grow well under humid climate which has more than 1600 mm of yearly precipitation. Is that true? Could anybody share some experience or tips with me?

Thanks in advance.